Early Q exchange... Castling necessary?

I believe very unnecessary. King stands better in the center to support his army without fear.

It really depends on whether the position is open or closed Josh Waitzkin told in a tuturial in chessmaster.

I think it depends if all other pieces are still on the board and if is an open game. In an open game I would castle for sure.

but if the position is closed I wouldn't castle. It may be a wasted move that could have been used for something else.

some I play with in real life, think it is really smart to delay castling and they have a really open position and sometimes I succeed in busting open the center as Josh Waitzkin told in chessmaster tutorial.

If I see a king stuck in the center I think "bust open the center"

unless the game is real close to the endgame I wouldn't like my king to be close to the center. The center is there the action is.

in the middle game I think one of the most important principles is king safty.

I think this would make a great topic for a video here on chess.com "when to castle and when not to."

It just depends on the position.  Figure out where your king needs to go, if it could do well in the center decide if your king in the middle will give rise to any tactics or mating attacks.  Also check what part of the board your rooks want to influence.  If castling sets up an ideal position faster then you should castle regardless of what pieces are on or off the board.  If bringing it to the center is the best way for king and rook regarding the position then do that regardless of what pieces are on or off the board.

Basically all the same stuff you consider whenever making any move or choosing any line of play -- that is you'll always go beyond rules of thumb.

I often don't castle after an early queen exchange because the king oftern become more active after this and access to the center sometimes becomes important- as always- depends on the game.